Absolutely crazy concept. But looks like they actually threw something decent together. I'd wager the bulk of problems people face with teeth come from poor flossing, this makes it effortless to avoid that.
I've owned water jets, the ones I've had suck. I always end up going back to dental floss. These days string on a plastic holder which I hate because it feels so wasteful to have all that single use plastic, but they are just so effective and I hate the manual wrapping of string, so I accept the wastefulness reluctantly.
This product potentially hits home with what I'd want from an effective waterjet, and it also comes with a brush on top.
The price is high, that's for sure, but I'm guessing they aren't aiming at the average electric tooth brush market, more like a competitor to the oral b io series 9 segment. And sure they are quite a bit above that price point, but they got a lot more of a solution backing the price.
My dentist recommended the dental picks (which can be used multiple times) instead of tape/string. I find it a lot easier than trying to fit my hands on my mouth (especially the longer L-shaped picks)